This invention relates to a method for producing hydrocarbons by reacting hydrogen gas eith carbon monoxide and/or gaseous carbon dioxide catalytically.
It is well known as the Fischer-Tropsch synthesis from many literatures to produce hydrocarbons by reacting hydrogen with carbon monoxide in the presence of a heterogeneous catalyst. The types of catalysts that have been studied for this and related processes include those based on metals or oxides of iron, cobalt, nickel, ruthenium, rhenium, thorium, rhodium, platinum and osmium. On the other hand, depending upon a catalyst and a reaction condition, the Fischer-Tropsch synthesis can be oriented predominantly to fuel oil, fuel gas such as methane, olefin such as ethylene, waxes or oxygen containing compounds such as alcohols. Consequently, the higher selectivity of desired products is advisable as well as a catalyst have high activity. The distribution of hydrocarbons obtained with a standard catalysts in the Fischer-Tropsch synthesis are fulfilled the Schulz-Flory distribution of molecular weights; the Fischer-Tropsch synthesis is regarded as a kind of polymerization wherein a chain growth occurs by a stepwise addition of active species containing one carbon atom adsorbed on a catalyst surface. Standard Fischer-Tropsch catalysts exhibit a nearly constant chain growth probability, which can be derived from Schulz-Flory plots and is obtained from the relationship between carbon number and the weight fraction of hydrocarbons per the carbon number, that is, these catalysts have low selectivity for the Fischer-Tropsch products. Therefore, it is necessary for us to develop the peculiar Fischer-Tropsch catalysts having non-Schulz-Flory distribution. It is well known from the recent literature (J.C.S. Chem Comm., 1095 (1979)) that Fischer-Tropsch synthesis of hydrocarbons over RuNaY-zeolite which can be prepared by an ion-exchange method shows a drastic change in chain growth probability in comparison with that over the standard Fischer-Tropsch catalysts. Herein, the roll of the zeolite is to control ruthenium metal particle size by cage dimensions in the zeolite. This means that the cage dimensions in the zeolite is used for controlling of the selectivity of Fischer-Tropsch products.